Someone typed cludonia. What went wrong?
heard as cludonia
spelled cladonia
The first vowel. It is a, not u: Cladonia.
What the ear did
A quick unstressed syllable at the front of a word is the easiest thing in the language to mishear, and u is one of the standard ways of writing that neutral sound. The name gives you no help, since the syllable carries no stress in any pronunciation.
C-L-A-D-O-N-I-A
The full entry for cladonia covers the name itself.